Shielded electrical connector systems have been widely used with electrical cables in electronics applications, such as data communications equipment, computers and digital information systems. Electrical plug connectors are typically used to terminate cables that have a multiplicity of electrically conductive signal leads or wires. In most applications, it is necessary to shield the signal-carrying conductors and circuits from electromagnetic interference (EMI) and/or radio frequency interference (RFI). Shielding is used to protect the conductors and circuits from both EMI that emanates from the different electronic components within a system as well as from outside sources.
To provide protection from such interference, electrical cables used in electronic equipment have shielding in the form of a sheath of conductive material between the outer cable jacket and the insulated conductors. The shielding can be formed from a variety of conductive materials, such as aluminum foil or braided copper wire.
Electrically conductive shields or shells are also placed around the terminal plug and socket connectors of the electrical cables. The plug and socket connectors form a shielded "input-output" connector system for cables which are designed to connect distinctly different and physically separated electronic components or equipment.
It should be generally understood for the purposes of the discussion herein that the plug connectors are mounted on the ends of multiconductor cables and that the socket connectors are mounted on stationary panels of the housings of various types of electronic equipment. It is, of course, possible to use either type of connector mounted on a cable or mounted on a piece of equipment.
A typical shielded plug connector has a plurality of electrical contacts that form the terminal ends of the cable. The contacts are mechanically positioned and retained within an insulating structure formed of dielectric material and are the functional part of the plug connector. The contacts are designed to be brought into intimate interconnection or mating with a counterpart socket which has complementary structural and electrical contact features. The shield for the plug connector is typically an electrically-conductive enclosure or shell that is connected to the shield sheath of the cable. The socket connector has a counterpart shield shell that is mateable with the plug shield shell. The socket shield shell is in electrical connection with the "shield" of the electronic equipment, i.e., the housing. Different mounting schemes for the socket shield shells are known in the art. The shield shells are typically fabricated using stamped and formed sheet metal. The shape of the shield shells can be varied. For example, the shield shells can be rectangular, circular, cylindrical, polygonal, etc.
An electrostatic discharge (ESD) can occur between two conductive bodies that are charged at different levels, thereby creating a potential difference. When the two bodies are brought into proximity, a discharge or spark can jump between them resulting in an electric current that can induce destructive effects in sensitive electronic circuitry, especially if no protective measures are taken. Sources for ESD may include the hands or body of a person handling electric cables or electronic equipment, as well as any metal, tools or incidental materials.
Three strategies are typically used for preventing damage caused by ESD. First, the sensitive circuits can be made less sensitive or vulnerable to ESD, so as to be capable of absorbing a discharge. Second, sensitive circuits can be insulated by means of physical barriers or separation from potential sources of ESD; for example, sufficiently thick layers of air and/or various dielectric material can be used. Third, the ESD can be provided with a means for being conducted away from sensitive circuitry to a location where it can be harmlessly dissipated. The present invention is intended to be employed in conjunction with this third strategy.
To protect against ESD, as well as the aforementioned EMI and RFI, the shielding used in electrical connector systems must sufficiently surround the electrical contacts so that, when the connectors are unmated, any ESD will discharge to the shielding rather than to the electrical contacts. It has been found, for a given arcing distance in air, that ESD is attracted to conductive objects with sharply pointed features, as compared with ones that which lack sharp points or edges. In other words, a discharge will preferentially strike the sharp feature.
In addition, for many electrical connector systems, a latching or locking mechanism is used to retain the plug and socket connectors in the mated position to prevent them from inadvertently separating and causing a system failure. In some cases, this mechanism may be incorporated in the shield shells of the respective plug and socket connectors. The latching or locking function may be accomplished by means of a "detent." For example, the plug connector can have one or more latching features projecting in a direction perpendicular to the direction of mating/unmating. The socket connector can have counterpart latching features designed to engage the plug latching features, thereby preventing a movement in the direction of unmating when the plug and socket connectors are fully mated.
As defined herein, a detent is a means for permitting releasable locking or latching of mateable connectors and for retaining the connectors in a fully mated position. Examples of different types of latching means include jackscrews, slide locks, wire bail locks, bayonets, snap rings, etc.
The manufacturing costs for the connector shields can contribute considerably to the total cost of a connector system. Moreover, electrical connectors are often used in appreciable numbers in a single electronic device, such as a computer or telecommunications apparatus. It is therefore desirable to reduce the cost of manufacture for electrical connectors by simplifying the design of the shielding.
In addition, the physical space constraints of increasingly compact electronic device designs have also significantly impacted the design of connectors. The result is that connectors must also be smaller and more compact. When designing ESD features and detent features for connectors, problems associated with achieving functionality and manufacturability can arise because of the size requirements. The present invention addresses these design problems by providing small and compact shield shells for electrical connectors that have novel ESD and detent features.
It is an object of the present invention to provide an electrical connector system having a mechanical detent feature that also acts as an attraction point for electrostatic discharge.
It is another object of the present invention to provide electrical connector shield shells that have a mechanical detent feature combined with an ESD feature that can be manufactured easily and at low cost.
It is still another object of the present invention to provide an electrical connector system that will not inadvertently separate or unmate.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be understood from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the elements recited and particularly pointed out in the claims.